I hate this mf

You missed 2 in the building in between the Experimental Feild Genorator boss and the broken bridge with another 2

And finally, during the first route of the South region of the New Institute side, it says pass through the broken building. Don't pass through but instead climb on top. You will find 2 more units.

One more is following the ones near the s**** south of the New Fontaine Research Institute. Follow the s**** from the second location until you reach ruins with a hydrogana puzzle and three switches. Destroy the pots near the water and below one there will be another unit, making it 70.

Another one that was missed is the near the Shrine of Depth. When you head up the slope from the ruins, make a short detour to the left where the tower is. To the left of it, you'll find one near a pile of debris.

This guide isn't entirely complete. If you go up Mont Esus East you will find 2 near the entrance to the tower and two behind the tower on a small ledge. So at least 4 more than the guide suggests, unless I have missed them while reading through it.